Regulation of growth and some key physiological processes in salt-stressed maize (Zea mays L.) plants by exogenous application of asparagine and glycerol

Maize seedlings were subjected to concentrations of 0 and 100 mM of NaCl in Hoagland's nutrient solution medium in plastic pots containing perlite. Two levels of asparagine (5 and 10 mM) and glycerol (20 and 40 mM) were sprayed onto the leaves of maize seedlings 10 days after germination. Saline stress caused considerable decline in total dry mass, chlorophyll content and relative water content in the maize plants. It increased the activities of superoxide dismutase, catalase and polyphenol oxidase as well as electrolyte leakage, but did not alter the activity of non-specific peroxidise. Foliar application of asparagine or glycerol was found to be effective in checking shoot growth inhibition under NaCl stress. Exogenously applied asparagine or glycerol reduced superoxide dismutase, non-specific peroxidase and polyphenol oxidase activities in salt-stressed maize plants compared to those not treated with these organic compounds. Salinity increased Na+ contents but reduced those of K+, Ca2+ and Pin the roots of the used genotype of maize. Foliar application of asparagine or glycerol increased the contents of K+, Ca2+ and P, but it reduced that of Na+ in salt-stressed maize plants as compared to those of the salt-stressed plants not supplied with glycerol or asparagine. Glycerol was more effective than asparagine in improving salinity tolerance of maize plants in terms of growth and physiological attributes measured in the present study.